Image shift correction for binocular virtual imaging apparatus

ABSTRACT

An imaging apparatus for stereoscopic viewing has a frame that seats against the head of a viewer. A left-eye imaging apparatus and a right-eye imaging apparatus are supported by the frame. The frame is reshapeable in a manner that changes a relative alignment of the left-eye imaging apparatus and the right-eye imaging apparatus to accommodate different viewer head anatomies. An adjustment mechanism responsive to the reshaping of the frame restores relative alignment of the left-eye imaging apparatus and the right-eye imaging apparatus for conveying stereoscopic virtual images to the viewer.

TECHNICAL FIELD

This disclosure generally relates to paired electronic displays worn bya viewer for forming left-eye and right-eye virtual images and moreparticularly relates to binocular near-eye displays within adjustablehead-mountable frames.

BACKGROUND

Head-Mounted Displays (HMDs) have been developed for a range of diverseuses, including military, commercial, industrial, fire-fighting, andentertainment applications. For many of these applications, there isvalue in forming a virtual image that can be visually superimposed overthe real-world image that lies in the field of view of the HMD user.

For stereoscopic imaging, virtual image content is generated anddisplayed for the left and right eyes of the viewer. To provide astereoscopic image, separate left and right-eye images are formedproviding slightly different perspectives of the image content andthereby lending an illusion of depth and volume to the displayedstereoscopic virtual image. Although providing images from slightlydifferent perspectives, the left- and right-eye images are aligned witheach other, so that the two images can be combined in the viewer's brainto give the perception of 3D depth.

To accommodate a viewer population having a range of head sizes, theframes of the HMD designs can be made adjustable. However, suchadjustments can disturb the alignment of the left- and right-eye imagesgenerated by the binocular near-eye displays mounted in the frames.Adjustments to the frame for improving viewer comfort and fit can reduceimage quality or increase eye strain.

One conventional approach specially adapts HMDs to individual users byproviding a stiff frame that allows adjustable mounting of displayelements over a range of positions. A separate alignment procedure canthen be used for each viewer, identifying suitable positioning ofcomponents for alignment of left- and right-eye images and mechanicallyfixing this positioning. This approach, however, does not adapt theframe for comfortably mounting on a viewer's head or allow a viewer toreadily share a head-mounted display with another viewer, since theindividual adjustments may not be well-suited to another viewer's visualanatomy.

SUMMARY

It is an object of the present disclosure to advance the art ofstereoscopic virtual image presentation when using compact head-mounteddevices and similar imaging apparatus. Advantageously, embodiments ofthe present disclosure feature stereoscopic imaging apparatus withadjustable frames to compensate for different viewer head dimensions andwith relatively adjustable near-eye displays that preserve opticalalignments required for presenting stereoscopic images over a range ofsuch frame adjustments.

These and other aspects, objects, features and advantages of thedisclosed embodiments will be more clearly understood and appreciatedfrom a review of the following detailed description of the preferredembodiments and appended claims, and by reference to the accompanyingdrawings.

According to an aspect of the present disclosure, there is provided animaging apparatus for stereoscopic viewing including a frame arranged toseat against the head of a viewer, a left-eye imaging apparatussupported by the frame, and a right-eye imaging apparatus supported bythe frame, wherein the left-eye imaging apparatus and the right-eyeimaging apparatus are relatively alignable to convey stereoscopicvirtual images to the viewer. The frame is reshapeable in a manner thatchanges a relative alignment of the left-eye imaging apparatus and theright-eye imaging apparatus to accommodate different viewer headanatomies. An adjustment mechanism responsive to the reshaping of theframe restores relative alignment of the left-eye imaging apparatus andthe right-eye imaging apparatus for conveying stereoscopic virtualimages to the viewer.

Preferably, the imaging apparatus further comprising at least one sensorcoupled to the frame and disposed to provide an output signal associatedwith the reshaping of the frame and indicative of the changes therelative alignment of the left- and right-eye imaging apparatus. Theadjustment mechanism preferably includes an actuator responsive to theoutput signal of the at least one sensor to adjust a relative angulardisposition of one or more components of the left- and right-eye imagingapparatus.

The at least one sensor can be arranged to measure flexure at a nosebridge of the frame or at one or both temples of the frame. Each of theleft-eye imaging apparatus and the right-eye imaging apparatus caninclude a waveguide that conveys the virtual image to the correspondingleft and right eye of the viewer. The actuator can be arranged to adjusta relative angular disposition of the waveguide of at least one of theleft-eye imaging apparatus and the right-eye imaging apparatus. Each ofthe left-eye imaging apparatus and the right-eye imaging apparatus canalso include a projector, and the actuator can be arranged to adjust arelative angular disposition of the projector with respect to thewaveguide of at least one of the left-eye imaging apparatus and theright-eye imaging apparatus.

The imaging apparatus can also include at least one image generator, andthe adjustment mechanism relatively shifts left-eye image content andright-eye image content produced by the image generator in response tothe output signal of the least one sensor signal.

According to another aspect of the present disclosure, there is providedan imaging apparatus for stereoscopic viewing including a flexible framethat seats against the head of a viewer and a left-eye imaging apparatusand a right-eye imaging apparatus that are relatively aligned to conveystereoscopic virtual images to the viewer. The left-eye imagingapparatus and the right-eye imaging apparatus are rigidly coupled toeach other within the frame. The left-eye imaging apparatus and theright-eye imaging apparatus remain relatively aligned to conveystereoscopic virtual images to the viewer when the flexible frame isbent into a different shape to better fit a head size of the viewer.

The flexible frame can include a flexible nose bridge located betweenthe left-eye imaging apparatus and the right-eye imaging apparatus, andthe left-eye imaging apparatus and the right-eye imaging apparatusremain relatively aligned to convey stereoscopic virtual images to theviewer when the flexible nose bridge is bent into a different shape tobetter fit a head size of the viewer. The left-eye imaging apparatus andthe right-eye imaging apparatus can be connected to the frame through apin in the flexible nose bridge. The flexible frame can include cavitieswithin which the left-eye imaging apparatus and the right-eye imagingapparatus are relatively movable with respect to the frame.

Another aspect of the invention includes a near-eye binocular imagingsystem including at least one image generator for generating images, aframe arranged to seat against the head of a viewer, a left-eye imagingapparatus supported by the frame for converting at least some of thegenerated images into virtual images viewable by a left eye the viewer,and a right-eye imaging apparatus supported by the frame for convertingat least some of the generated images into virtual images viewable by aright eye the viewer. The left-eye imaging apparatus and the right-eyeimaging apparatus are relatively oriented for relatively aligning thevirtual images viewable by the left and right eyes of the viewer toconvey stereoscopic virtual images to the viewer. The frame isreshapeable in a manner that changes the relative orientation of theleft-eye imaging apparatus and the right-eye imaging apparatus toaccommodate different viewer head anatomies while correspondinglymisaligning the virtual images viewable by the left and right eyes ofthe viewer. A sensor supported by the frame detects and outputs anindication of the change in the relative orientation of the left-eyeimaging apparatus and the right-eye imaging apparatus. A processorassociated with the at least one image generator receives the outputfrom the sensor, determines an amount of adjustment to compensate forthe changes the relative orientation of the left-eye imaging apparatusand the right-eye imaging apparatus, and provides for shifting theimages that are generated by the at least one image generator forrestoring of the relative alignment of the virtual images viewable bythe left and right eyes of the viewer to convey stereoscopic virtualimages to the viewer.

The left-eye imaging apparatus together with a first of the at least oneimage generator can comprise a first projector and a first waveguidesupported by the frame. The first projector incorporates the first imagegenerator and provides for projecting images generated by the firstimage generator as virtual images into the first waveguide, and thefirst waveguide provides for conveying the virtual images to theviewer's left eye. The right-eye imaging apparatus together with asecond of the at least one image generator can comprise a secondprojector and a second waveguide supported by the frame. The secondprojector incorporates the second image generator and provides forprojecting images generated by the second image generator as virtualimages into the second waveguide, and the second waveguide provides forconveying the virtual images to the viewer's right eye. The processorcan provide for shifting the images generated by at least one of thefirst and second image generators for conveying stereoscopic virtualimages to the viewer. Alternatively, the processor can provide forshifting the images generated by both the first and second imagegenerators for conveying stereoscopic virtual images to the viewer.

The frame can be subject to flexure for accommodating different viewerhead anatomies, and the sensor can provide for measuring the flexure ofthe frame. The sensor can include at least one of a camera and adistance sensor mounted on the frame for measuring the flexure of theframe. The frame can include both a frame front supporting the first andsecond waveguides and temples supporting the first and secondprojectors. In addition, the frame front can include a nose-piecesection between the first and second waveguides, and the sensor can bearranged to detect flexure of the nose-piece section. Alternatively, thesensor can be one of at least two sensors for detecting changes in theorientation of the temples with respect to the frame front.

Another aspect as a method accommodates flexure of a frame that supportsa left-eye imaging apparatus and a right-eye imaging apparatus withinwhich images generate by an image generator are converted into virtualimages that are viewable by the left and right eyes of a viewer. Theleft-eye imaging apparatus and the right-eye imaging apparatus arerelatively orienting for relatively aligning the virtual images viewableby the left and right eyes of the viewer to convey stereoscopic virtualimages to the viewer. The frame is reshaped in a manner that changes arelative orientation of the left-eye imaging apparatus and the right-eyeimaging apparatus to accommodate different viewer head anatomies whilecorrespondingly misaligning the virtual images viewable by the left andright eyes of the viewer. The reshaping of the frame is sensed as anindication of the change in the relative orientation of the left-eyeimaging apparatus and the right-eye imaging apparatus. An amount ofadjustment to compensate for the changes the relative orientation of theleft-eye imaging apparatus and the right-eye imaging apparatus isdetermined from the sensed reshaping of the frame. The images that aregenerated by the at least one image generator are shifted in accordancewith the determined amount of adjustment for restoring of the relativealignment of the virtual images viewable by the left and right eyes ofthe viewer for conveying stereoscopic virtual images to the viewer.

The reshaping of the frame can include bending a nose-piece portion ofthe frame between the left-eye and right-eye imaging apparatus and thereferenced sensing can detect the bending of the nose-piece section. Theat least one image generator can include a first image generator forgenerating images for the left-eye imaging apparatus and a second imagegenerator for generating images for the right-eye imaging apparatus. Thereferenced shifting can include shifting the images generated by thefirst and second image generators in opposite directions for conveyingstereoscopic virtual images to the viewer.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1A is a schematic diagram of a head-mounted display (HMD) forforming a stereoscopic virtual image pair for a viewer.

FIG. 1B is a schematic diagram of the HMD of FIG. 1A with right- andleft-eye images misaligned.

FIGS. 2A, 2B, and 2C are top views of a HMD in a schematic formincluding imaging components in different orientations and relativeeffects on the orientations of left- and right-eye virtual images.

FIGS. 3A, 3B, and 3C are top views of a HMD having waveguide typeimaging components and an eyeglass frame subject to flexure resulting indifferent orientations of left- and right-eye virtual images.

FIG. 4A is a top sectional view of a HMD with adjustable imagingcomponents within a flexible frame.

FIG. 4B is a top sectional view of the HMD of FIG. 4A showing the framein a flexed position.

FIG. 5 is a perspective view of a HMD for stereoscopic augmented realityviewing using aspects of the present disclosure.

FIG. 6A is a top, cut-away view of a flexible frame and embedded imagingsystem.

FIG. 6B is a top, cut-away view of the flexible frame and embeddedimaging system of FIG. 6A where the frame has been bent.

FIG. 7 is a top view of a HMD with a frame having rigid and flexibleportions.

FIG. 8 is a top view of an AR/VR system showing the positioning of aflex rotation axis.

FIG. 9 is a front view of an AR/VR system with a flex rotation axis.

FIG. 10 is a side view illustrating the righthand side of an AR/VRsystem and the orientation of a flex rotation axis.

DETAILED DESCRIPTION

The present description is directed to various combinations of elementsforming part of, or cooperating more directly with, apparatus inaccordance with the present teaching. It is to be understood thatelements not specifically shown or described may take various forms wellknown to those skilled in the art.

Where they are used herein, the terms “first”, “second”, and so on, donot necessarily denote any ordinal, sequential, or priority relation,but are simply used to more clearly distinguish one element or set ofelements from another, unless specified otherwise.

In the context of the present disclosure, the terms “viewer”,“operator”, and “user” are considered to be equivalent and refer to theperson who wears and views images using the HMD viewing device.

The term “actuable” has its conventional meaning, relating to a deviceor component that is capable of effecting an action in response to astimulus, such as in response to an electrical signal, for example.

The phrase “optical infinity” as used herein corresponds to conventionalusage in the camera and imaging arts, indicating image formation usingsubstantially collimated light, so that the focus distance exceeds atleast about 4 meters.

In the context of the present disclosure, the term “coupled” is intendedto indicate a physical association, connection, relation, or linking,between two or more components, such that the disposition of onecomponent affects the spatial disposition of a component to which it iscoupled. For mechanical coupling, two components need not be in directcontact, but can be linked through one or more intermediary components.A component for optical coupling allows light energy to be input to, oroutput from, an optical apparatus.

An “embedded” object or component here means that a portion of theobject or component is within another object or component. It is nothere used to imply that the object or component is completely covered byanother object or component.

As an alternative to real image projection, an optical system canproduce a virtual image display. In contrast to methods for forming areal image, a virtual image is not formed on a display surface. That is,if a display surface were positioned at the perceived location of avirtual image, no image would be formed on that surface. Virtual imagedisplay has inherent advantages for augmented reality display. Forexample, the apparent size of a virtual image is not limited by the sizeor location of a display surface. In comparison with systems thatproject a real image, a more realistic viewing experience can beprovided by forming a virtual image that appears to be some distanceaway. Providing a virtual image also obviates any need to compensate forscreen artifacts, as may be necessary when projecting a real image.

FIGS. 1A and 1B show a head-mounted display HMD 10 for forming astereoscopic virtual image pair 20 for a viewer. HMD 10 forms a left-eyevirtual image 22 l and a right-eye virtual image 22 r, appropriatelyaligned with each other at a distance in front of the HMD 10 to providethe advantages of stereoscopic presentation. In FIG. 1A, left-eye image22 l and right-eye image 22 r are represented as being aligned forstereoscopic imaging. In FIG. 1B, left-eye image 22 l and right-eyeimage 22 r are positioned out of horizontal alignment, as shown inexaggerated form.

The virtual images output from the HMD 10 comprise overlapping beamswithin which the virtual images are angularly encoded. Preferably, thebeams corresponding to matching points within the left- and right-eyeimages 22 l and 22 r are aligned with each other or otherwise convergetoward common points in the space in front of the HMD to support thedesired stereoscopic presentation. Thus, the HMD 10 is preferablyconstructed to maintain the desired angular relationships between theleft-eye image 22 l and right-eye image 22 r.

HMDs are preferably adjustable so that the HMDs can be comfortably andeffectively worn by viewers with different head sizes or with otheranatomical variations, including variations in interpupillary distance,that affect the way in which the wearable displays are optimallymountable on the viewers' heads. Embodiments of the present disclosurecan accommodate the reshaping of HMDs for fitting different viewer headanatomies while preserving the desired stereoscopic presentation to eachso-fitted viewer.

The top view schematics of FIGS. 2A, 2B, and 2C show changed positionsof left- and right-eye virtual images corresponding to changes in therelative position of imaging components of head mounted display 10, suchas changes due to flexure of an eyeglass frame F or other mountingapparatus. Head mounted display 10 has a left-eye imaging apparatus 12 land a right-eye imaging apparatus 12 r. Each imaging apparatus 12 l, 12r has image-forming optics, such as a corresponding lens L1 l or L1 rand a corresponding image generator 14 l or 14 r. Each image generator14 l, 14 r is positioned at approximately focal length distance from itscorresponding lens L1 l, L1 r for forming an infinity-focused virtualimage 22 l, 22 r for the corresponding eye El or Er.

FIG. 2A shows forming the left- and right-eye virtual images 22 l and 22r at an intended position for stereoscopic viewing. FIG. 2B showsangular shifting of images 22 l and 22 r due to flexure of frame F alonga nose bridge 34. FIG. 2C shows a correction in the orientation of theimages 22 l and 22 r to compensate for frame F flexure. The flexure offrame F shown in FIG. 2B corresponds to a flexure that might be used toadapt the frame F to fit a smaller head size with a result that theimages 22 l and 22 r shift away from each other requiring a correctionsuch as shown in FIG. 2C to preserve a desired stereoscopicpresentation.

FIGS. 3A, 3B, and 3C show a HMD with a more complete frame F like aconventional eyeglass frame but depict the formation of just theright-eye image 22 r for simplicity. The frame F has a frame front Ffand left and right temples Tl and Tr. A left-eye image is assumed toalso be formed in a symmetric manner. The right-eye imaging apparatusincludes an image generator in the form of a projector 32 mounted on thetemple Tr and a plane-parallel waveguide 40 mounted on the frame frontFf. The projector 32 is oriented to direct angularly encodedimage-bearing beams into the waveguide 40 along a nominal inputdirection represented by dashed arrow 26. The waveguide 40 conveys theimage-bearing beams, such as by total internal reflection, to an outputposition in front of the right eye Er, where the image-bearing beams aredirected out of the waveguide 40 and into the right eye Er along anominal output direction represented by dashed arrow 28. Both thenominal input direction 26 and the nominal output direction 28 are shownaligned with a normal N of the waveguide 40, which also corresponds tothe nominal orientation of the virtual image 22 r. Other startingorientations of the nominal input and output directions 26 and 28 arepossible but the alignments with the normal N provide a ready point ofreference for comparison with the differing orientations of FIGS. 3B and3C.

In FIG. 3B, the frame F is reshaped, e.g., bent, to fit a viewer with asmaller head size. The main effect of the flexure is a change in theorientation of the right temple Tr with respect to the frame front Ff.The direction of movement of the right temple Tr for fitting a smallerhead size is indicated by arrow 36. With the projector 32 mounted on theright temple Tr, the indicated flexure changes the nominal inputdirection 26 along which the image-bearing beams from the projector 32enter the waveguide 40. Due to the regular symmetries of the waveguide40, the nominal output direction 28 along which the image-bearing beamsexit the waveguide 40 shifts in an equal but opposite angular direction,whereby the projected virtual image 22 r is moved inward with respect tothe viewer field of view (FOV). Note that this is the opposite effect tothat shown in FIG. 2B, where the entire imaging apparatus (e.g., theprojector together with the waveguide) is pivoted about the nose bridge34 to accommodate a smaller size viewer head. Thus, distributingflexures between the nose bridge 34 and temples Tl and Tr can be used toaccommodate smaller head sizes while maintaining the desired alignmentsbetween the projected left and right virtual images 22 l and 22 r.

As FIG. 3C shows, the opposite movement of virtual image 22 r happenswhen the temples such as the temple Tr, are bent in an oppositedirection as shown by arrow 38 to accommodate a viewer with a largerhead size. For example, the virtual image 22 r is shown to move outwardwithin the viewer field of view (FOV) in accordance with the change inthe nominal input direction 26 that accompanies the relative outwardpivotal movement of the projector 32 with the temple Tr in the directionof arrow 38.

Using either the HMD design of FIGS. 2A-2C or that of FIGS. 3A-3C,manual adjustment can be used to reposition components of left and rightimaging apparatus 12 l and 12 r for correcting misalignments between theleft- and right-eye virtual images 22 l and 22 r associated with viewerhead-accommodating flexures of the HMD frames F. However, such manualadjustment can be time-consuming and the need for a manual adjustmentprocedure for each individual viewer can have a negative impact on theoverall usability of a HMD. In response to the need to readilyaccommodate different viewers with the same HMD, an embodiment of thepresent disclosure provides an automated adjustment mechanism thatmeasures flexure of the frame F and automatically computes and adjustsfor left- and right-eye virtual image misalignments associated with theneed to fit the different head sizes of viewers.

Referring to the top view schematic of FIGS. 4A and 4B, a HMD 50 isarranged to compensate for measured frame flexure and correspondingviewer head dimensions by changing the angular alignments of componentsin the left- and right-eye imaging apparatus 12 l and 12 r. In the HMD50, flexure of frame F is sensed using a sensor 52, such as a straingauge or other suitable position sensing device. The signal receivedfrom sensor 52, indicative of the amount of frame flexure and of therelative amount of corresponding image positioning adjustment needed forleft- and right-eye image alignment, is processed by a control logicprocessor 54, such as a microcontroller. Output signals generated fromprocessor 54 control one or both actuators 60 for adjusting thepositions of one or more components within the left and right-eyeimaging apparatus 12 l and 12 r. For example, this position adjustmentcan change the angular orientation of lens elements L1 l and L1 r.Alternatively, the adjustment can change the orientation or behavior ofsome other component in the imaging path, including a waveguide orprojector, thereby suitably shifting the relative positions of the left-and right-eye virtual images 22 l and 22 r. Stereoscopic viewing can becorrected by moving just one of the left- and right-eye virtual images22 l and 22 r, but preferably, both virtual images 22 l and 22 r aremoved to maintain the stereoscopic image at a desired position (e.g.,centered) within the field of view and to divide the required amount ofcorrection between the components of the left and right-eye imagingapparatus 12 l and 12 r.

The sensor 52 can be a strain gauge that provides an output signal basedon sensed flexure of the nose-piece section of frame F that lies betweenleft- and right-eye imaging apparatus 12 l, 12 r. Alternative oradditional sensors 56 can be used to sense deformations at the templesTl and Tr or between the temples Tl and Tr and the frame front Ff.Control logic processor 54, in signal communication with sensors 56,converts the received signal to a digital input value and uses thevalues to determine a value for adjusting the angular orientation of thelenses L1 l and L1 r, such as from a pre-calculated or empiricallyderived look-up table (LUT).

An alternative to or in addition to such a mechanical adjustment ofimaging components, the encoding of the virtual images within theirangularly encoded beams can be adjusted within the image projectionsoftware. For example, images generated within the projectors can berelatively shifted before being converted into the angularly encodedbeams output from the projector so that the resulting virtual images arerelatively displaced within the viewer's FOV. Based on sensedinformation from one or more sensors 52, 56, control logic of processor54 adjusts the image content to shift the relative left/right positionof the virtual images 22 l and 22 r according to the sensed frameflexure. That is, pixels within the virtual images can be appropriatelyshifted left or right according to the sensed condition.

Various types of sensing and actuation devices can be used to providesignal output used for angular correction of one or more opticalcomponents or, alternately, control logic adjustment of the image data.Sensor types can include strain gauge sensors, rotation sensors, Halleffect sensors, limit switches, or other devices. Alternatively oradditionally, the sensor 52 can be an operator control or switch, suchas a thumbwheel switch, that senses a viewer adjustment for manualcontrol of left/right image alignment.

The perspective view of FIG. 5 shows a binocular display system 100 forthree-dimensional (3-D) augmented reality viewing. Display system 100 isshown as an HMD with left-eye imaging system 12 l having a pupilexpander 1401 for the left eye and corresponding right-eye imagingsystem 12 r having a pupil expander 140 r for the right eye. The pupilexpanders 1401 and 140 r expand areas of overlap between the angularlyencoded image-bearing beams directed toward the viewer's eyes withinwhich areas the intended virtual images can be seen. The pupil expanders1401 and 140 r, which are preferably incorporated in the otherembodiments, provide for accommodating variations in interpupillarydistances among different viewers.

One or more image sources 152, such as a picoprojector or similardevice, generate a separate image for each eye, formed as a virtualimage with the needed image orientation for upright image display. Oneor more sensors 52 provide signals indicative of needed adjustment foralignment of left-eye and right-eye images. The images that aregenerated can be a stereoscopic pair of images for 3-D viewing. Thevirtual image that is formed by the optical system can appear to besuperimposed or overlaid onto the real-world scene content seen by theviewer. Additional components familiar to those skilled in the augmentedreality visualization arts, such as one or more cameras mounted on theframe of the HMD for viewing scene content or viewer gaze tracking, canalso be provided.

FIGS. 6A and 6B are diagrams showing top sectional views of a HMD in theform of a flexible frame AR/VR (augmented reality or virtual reality)system 200. Flexible frame AR/VR system 200 comprises a flexible nosebridge 206 to which is attached left eye frame portion 202 and right eyeframe portion 204. A left temple assembly 208 is rigidly attached toleft eye frame portion 202 and a right temple assembly 210 is rigidlyattached to right eye frame portion 204. Within flexible nose bridge 206there is attached a support pin 220 that supports a support fixture 222.Support pin 220 and support fixture 222 do not move when flexible nosebridge 206 is flexed. Support fixture 222 supports a left exit window224 and right exit window 226 of a left- and right-eye imaging apparatusand maintains the left exit window 224 and right exit window 226 in afixed angular relationship to each other when flexible nose bridge 206is flexed. Left eye frame portion 202 has a left cavity 228 into whichleft exit window 224 is disposed. Right eye frame portion 204 has aright cavity 230 into which right exit window 226 is disposed. The leftand right cavities 228 and 230 accommodate flex of flexible nose bridge206 without transferring any significant mechanical force, pressure,stress or strain onto left exit window 224 or right exit window 226. Inthis way, left and right eye frame portion 202 and 204 may move withoutchanging the angular relations between left and right exit windows 224and 226.

Flexible frame AR/VR system 200 further comprises a left imaging pathwith left optical components 236 coupled to left exit window 224 by leftoptical attachment element 232. Flexible frame AR/VR system 200 furthercomprises a right imaging path with right optical components 238 coupledto right exit window 226 by right optical attachment element 234. In onearrangement, one or both the left optical component 236 and the rightoptical component 238 are a prism. In another arrangement, one or boththe left optical component 236 and the right optical component 238 are acomposite prism or an assembly of multiple prisms. In anotherarrangement, one or both the left optical component 236 and the rightoptical component 238 are a prism have one or more prisms and one ormore mirrors.

The left optical component 236 is optically and mechanically coupled toleft projection system 244, and the right optical component 238 isoptically and mechanically coupled to right projection system 246 alongtheir respective imaging paths. A left channel 240 allows the leftoptical components 236 to extend into the left eye portion of frame 202,and a right channel 242 allows the right optical components 238 toextend into the right eye portion frame 204 such that flex motion of theleft and right eye frames 202 and 204 does not impart significant force,pressure, stress or strain onto left and right optical components 236and 238. The left and right projection systems 244 and 246 are disposedin left and right temple frame cavities 248 and 250, respectively, suchthat flex movement of the left and right temple assemblies do not impartany significant force, pressure, stress, or strain onto left or rightprojection systems 244 or 246 respectively. Because of this, relativepositions of left and right-eye imaging apparatus are not changed as theflexible nose bridge 206 is flexed.

Flexible frame AR/VR system 200 further has left system components 252and right system components 254 rigidly attach to the left templeassembly 208 and the right temple assembly 210, respectively, andtherefore, move with the left and right temple assemblies 208 and 210when these temple assemblies are bent (flexed) to accommodate a wider ornarrower viewer head sizes in relation to a nominal viewer head size atwhich the left and right temple assemblies remain unflexed. The left andright system components 252 and 254 can include one or more of abattery, a circuit board, and a touch pad, as well as other componentsknown to be associated with AR/VR systems.

FIGS. 6A and 6B further show a left frame surface normal 300 and a leftexit window surface normal 302 as well as a right frame surface normal304 and a right exit window surface normal 306. As shown in FIG. 6A, theleft frame and left window normals 300 and 302 are aligned and the rightframe and right window normals 304 and 306 are aligned when no externalforces applied to bend the flexible nose bridge 206.

However, as shown in FIG. 6B, externally applied flex forces (shown asarrows at the left and right temple assembly portions 208 and 210) bendthe flexible nose bridge 206. As a result, the left frame normal 300 isnow seen to be inclined with respect to the left exit window normal 302.Similarly, the right frame normal 304 is inclined with respect to theright exit window normal 306. Because of the mechanically rigidconnection of the support pin 220, the support fixture 222, the left andright exit windows 224, 226, the left and right optical components 236,238, and the left and right projection systems 244, 246 together withthe clearance provided by the left and right cavities 228, 230, the leftand right channels 240, 242, and the left and right temple cavities 248,250, the externally applied force bends the nose bridge 206 withoutchanging the relative dispositions of the various optical componentscomprising the left-eye imaging apparatus and the right-eye imagingapparatus. The required clearance can be created in a variety of waysincluding fashioning the cavities as slots that permit relative motionof the frame with respect to the fixed optical components in thedirections intended for flexure.

FIG. 7 is a top view of a HMD in the form of an AR/VR system 400 havinga having a frame front Ff including a left exit window portion 402 and aright exit window portion 404 joined by a nose bridge 406. Each of thetwo temples Tl and Tr are divided into two portions distinguished bydimension lines. The left temple Tl includes a front temple portion 410and a rear temple portion 420. The right temple Tr includes a fronttemple portion 412 and a rear temple portion 424. The AR/VR system 400also includes a left-eye imaging apparatus and a right-eye imagingapparatus. The left-eye imaging apparatus includes a waveguide 430 fixedwithin the left exit window portion 402 and a projector 432 fixed to thefront temple portion 410. Similarly, the right-eye imaging apparatusincludes a waveguide 440 fixed within the right exit window portion 404and a projector 442 fixed to the front temple portion 412.

The frame front, including the left exit window portion 402, the rightexit window portion 404, and the nose bridge 406, and the front portions410 and 412 of the left and right temples Tl and Tr form a rigidstructure for maintaining proper alignments between the left-eye imagingapparatus and the right-eye imaging apparatus for supportingstereoscopic presentations. A rigid nose piece 406, together with rigidconnections between the nose piece 406 and both the left exit windowportion 402 and the right exit window portion 404, maintains a fixedangular relationship between the two waveguides 430 and 440. A rigidconnection between the left exit window portion 402 and the frontportion 410 of the left temple Tl maintains a fixed angular relationshipbetween the waveguide 430 and the projector 432. Similarly, a rigidconnection between the right exit window portion 404 and the frontportion 412 of the right temple Tr maintains a fixed angularrelationship between the waveguide 440 and the projector 442.

Unlike the front portions of the frame, the rear temple portions 420 and424 are flexible with respect to the front temple portions 410 and 412to accommodate different viewer head widths. For example, the reartemple portions 420 and 424 can be fabricated from one or more flexibleelastic materials, having elastic memory, that when laterally displacedspring back to a nominal position when no external forces are applied tothe rear temple portions 420 and 424. Alternatively, the left and rightthe rear temple portions 420 and 424 can be respectively connected tothe left and right front temple portions 410 and 412 with spring-loadedor elastomeric hinges. The left and right the rear temple portions 420and 424 could also be subdivided into flexibly interconnected sections.Regardless of the mode of flexibility whereby the rear temple portions420 and 424 are urged against viewers' heads of different widths, theflexibility and variable dispositions of the rear temple portions 420and 424 do not affect the alignments between the left-eye imagingapparatus and the right-eye imaging apparatus for supportingstereoscopic presentations.

FIG. 8 is a top view of AR/VR system 400 showing the positioning of aflexible hinge rotation axis 454 in the nose bridge 406 region of AR/VRsystem 400. The left fixed exit window portion 402 and right fixed exitwindow portion 404 are constructed and joined together in the nosebridge 406 region such that they can rotate about the hinge rotationaxis 454 but no other axis. Such rotation about the hinge rotation axis454 may be used to compensate for the various head sizes of differentwearers of the AR/VR system 400. Flex rotation (rotation of each left,right half of AR/VR system 400 in opposite directions) about the hingerotation axis 454 rotates the left fixed exit window portion 402 and theright fixed exit window portion 404 that are rigidly attached to theleft fixed frame portion 410 and the right fixed frame portion 412,respectively, in opposite directions. The nose bridge 406, together withembedded hinge assembly (not shown, but see 520 of FIG. 9 ) isconstructed to prevent twist and/or torque motion between the left fixedexit window portion 402 and the right fixed exit window portion 404about any axis except the axis defined by the hinge rotation axis 454.Such flex rotation shifts the left virtual image plane 446 and the rightvirtual image plane 448 left or right. These shifts of virtual imageplanes can be compensated for in software that generates the images tobe displayed through left planar waveguide 430 and right planarwaveguide 440.

Hinge rotation axis 454 may be defined by the intersection of two planesto form a line, the line being the hinge rotation axis 454. The firstplane is left plane 450 parallel to the left virtual image plane 446 andthe second plane is right plane 452 parallel to the right virtual imageplane 448 such that the intersection of left plane 450 and right plane452 defines a line running through the nose bridge 406 region of AR/VRsystem 400. The left virtual image plane 446 is generated by the leftplanar waveguide 430 and the right virtual image plane is generated bythe right planar waveguide 440. The left virtual image plane 446 may notbe parallel to the left planar waveguide 430, and right virtual imageplane 448 may not be parallel to the right planar waveguide 440.

FIG. 9 is a front view of an AR/VR system 500 having a right exit windowframe 510, a left exit window frame 512 and a nose bridge 514. Embeddedwithin the right exit window frame 510 is a planar waveguide (not shownbut see 440 of FIG. 8 ) and embedded within the left exit window frame512 is a planar waveguide (not shown but see 430 of FIG. 8 ). Embeddedhinge assembly 520 is disposed within nose bridge 514 and is furthermechanically connected to right exit window frame 510 and mechanicallyconnected to left exit window frame 512 such that the right exit windowframe 510 and the left exit window frame 512 can pivot about the hingerotation axis 530 thus rotating the embedded planar waveguides (notshown) about the hinge pin rotation axis 530. The hinge rotation axis530 has been defined in FIG. 8 as hinge rotation axis 454. In this way,the embedded planar waveguides (see 430, 440 of FIG. 8 ) are alsorotated about hinge rotation axis 530.

Embedded hinge assembly 520 may consist of a mechanical pin 522, lefttab 526 and right tab 524 such that the left tab 526 and right tab 524may rotate about mechanical pin 522. Mechanical pin 522 is positionedand aligned along hinge pin rotation axis 530 (which is the same ashinge rotation axis 454 of FIG. 8 ). Embedded hinge assembly 520 mayconsist of right tab 524 and a left tab 526. Right tab 524 may have acylinder-shaped edge (not shown) and an essentially flat tab section(not shown). Left tab 526 may have a receptacle groove edge (not shown)and an essentially flat tab section (not shown). The cylinder-shapededge of right tab 524 may slide into receptacle groove edge of left tab526 to form hinge assembly 520. Cylinder shaped edge of right tab 524 isaligned along hinge pin rotation axis 530. Cylinder shaped edge of righttab 524 may be magnetic. Receptacle edge groove edge of left tab 526 maybe magnetic and/or composed of a material that is magnetizable. Hingeassembly 520 may be constructed in two halves that can be repeatablyjoined and separated by the wearer of AR/VR system 500. Hinge assembly520 may be constructed in at least two part (right and left parts) suchthat right part is a continuous part of right exit window frame 510 andleft part is a continuous part of left exit window frame 512. As isknown to those skilled in the art, there are other ways to construct ahinge like mechanism suitable for allowing right exit window frame 510and left exit window frame 512 to rotate, in opposite rotationdirections, about hinge pin rotation axis 530 and no other axis whilepreventing twists between left exit window frame 512 and right exitwindow frame 510.

FIG. 10 is a side view illustrating the righthand side of AR/VR system500 comprising at least a right exit window frame 510, a right exitwindow 552, embedded right planar waveguide (not shown, but see 440 ofFIG. 8 ) and a right temple frame 540. Right temple frame 540 furthercomprises a right fixed temple frame 544 portion and a right rear frame542 portion. Right rear frame 542 may be constructed from known flexiblematerial. Right rear frame 542 may be constructed into individualconnected sections, one or more sections may be able to flex while othersections may be rigid. Right temple frame 540 is rigidly connected toright exit window frame 510 by rigid frame connection 550.

FIG. 10 further illustrates the relative orientation of hinge pinrotation axis 530. Vertical line 562 and horizontal line 560 areorthogonal to one another and are used for descriptive orientationpurposes only. Horizontal line 560 may not be perpendicular to line 570formed by the intersection of left virtual image plane and right virtualimage plane. As shown, the hinge pin rotation axis 530 is parallel toline 570 and is at a tilt angle 582 to the vertical line 562. Tilt angle582 may be an angle within the angular range 5 to 10 degrees. Tilt angle582 may be within the angular range of 0 to 15 degrees. Tile angle maybe within the angular range of −15 to +15 degrees.

FIG. 10 is illustrative of the right half of the AR/VR system 500. It isto be understood that similar construction and quantities are to beapplied to the left half of the AR/VR system 500, with mirror symmetry.

The flex of the AR/VR system 500, due to the constraints caused by theconstruction of the embedded hinge assembly 520, permits the right andleft frame halves of the AR/VR system 500 to be rotated about the hingepin rotation axis 530 in opposite rotation directions to accommodatedifferent wearer's head sizes.

The angular amount that the embedded planar waveguide (not shown but see430 of FIG. 8 ) within left exit window frame 512 and the embeddedplanar waveguide (not shown but see 440 of FIG. 8 ) within right exitwindow frame 510 are rotated about hinge pin rotation axis 530 can bedetermined in several different ways. One way is to include anelectronic sensor element within hinge assembly 520 of FIG. 9 that cansense the angular amount of rotation about the hinge pin rotation axis530. (See sensor 52 in FIG. 4A and FIG. 4B.) Another way to determinethe angular rotation of the embedded waveguides is by utilization of aforward looking camera 602 of FIG. 9 embedded, for example, in the righthalf of the AR/VR system 500, and a forward looking distance sensor 600of FIG. 9 embedded within the left half of the AR/VR system 500 suchthat the camera 602 and distance sensor 600 are rotated with therotation of the embedded waveguides about the hinge pin rotation axis530. The camera 602 may provide the angular orientation to a distantobject placed in front of the AR/VR system 500 relative to the camera'svector normal direction, while the distance sensor 600 may provide theangular orientation to the same object with respect to the vector normalof the distance sensor as well as the distance to the object. With thesethree measurements, and the known construction of the AR/VR system 500,including camera 602 and distance sensor 600 locations within AR/VRsystem 500, the angular orientation of the left and right embeddedwaveguides about the hinge pin rotation axis 530 can be determined. Oncethe angular rotation amount about the hinge pin rotation axis 530 isdetermined, the angular rotation amount may be utilized by software suchthat the left and right virtual images may be shifted horizontally bythe software generating the left and right virtual images to compensatefor the planar waveguides relative orientation to one another, providinga 3-dimensional virtual image to the wearer of AR/VR system 500.

Alternatively, the relative rotation of the fixed exit window portions402 and 404 can take place about the hinge rotation axis 454 (or 530)independently of the waveguides 430 and 440 and their relativeorientations to the respective projectors 432 and 442 such as shown inthe system 200 in FIGS. 6A and 6B for accommodating different anatomieswithout changing the angular relations between the left virtual imageplane 446 and the right virtual image plane 448. The amount that thefixed exit window portions 402 and 404 can be pivoted independently ofthe waveguides 430 and 440 can be limited to preserve the angularrelations between the left virtual image plane 446 and the right virtualimage plane 448 for small adjustments but to vary he angular relationsbetween the left virtual image plane 446 and the right virtual imageplane 448 for larger adjustments.

The description highlights presently preferred embodiments, but it willbe understood that variations and modifications can be effected withinthe spirit and scope of the overall teaching. The presently disclosedembodiments are therefore considered in all respects to be illustrativeand not restrictive, and all changes that come within the meaning andrange of equivalents thereof are intended to be embraced therein.

The invention claimed is:
 1. An imaging apparatus for stereoscopicviewing, comprising: a frame operable to be reshaped from a first shapeto a second shape; a left-eye imaging apparatus supported by the frame,wherein the left-eye imaging apparatus comprises a first projector and afirst waveguide; a right-eye imaging apparatus supported by the frame,wherein the right-eye imaging apparatus comprises a second projector anda second waveguide; wherein the left-eye imaging apparatus and theright-eye imaging apparatus have a first relative alignment operable toconvey stereoscopic virtual images to a viewer when the frame is in thefirst shape, wherein the left-eye imaging apparatus and the right-eyeimaging apparatus are arranged at a second relative alignment when theframe is in the second shape; and an adjustment mechanism comprising anactuator operable to respond to a reshaping of the frame, wherein theactuator is operable to change an angular alignment of the firstprojector relative to the first waveguide and the frame and/or thesecond projector relative to the second waveguide and the frame torestore the first relative alignment of the left-eye imaging apparatusand the right-eye imaging apparatus while the frame is in the secondshape.
 2. The apparatus of claim 1, further comprising at least onesensor coupled with the frame and operable to provide an output signalindicative of the changes to a relative alignment of the left-eyeimaging apparatus and the right-eye imaging apparatus between the firstrelative alignment and the second relative alignment.
 3. The apparatusof claim 2, wherein the actuator is operable to respond to the outputsignal of the at least one sensor, wherein the actuator is operable toadjust a relative angular disposition of one or more components of theleft-eye imaging apparatus and the right-eye imaging apparatus.
 4. Theapparatus of claim 3, wherein the at least one sensor measures flexureat a nose bridge of the frame.
 5. The apparatus of claim 3, wherein theframe comprises a left temple and a right temple, and the at least onesensor is operable to measure flexure at one or both temples.
 6. Theapparatus of claim 3, wherein the at least one sensor is a strain gauge.7. The apparatus of claim 3, wherein the at least one sensor is anoperator control.
 8. The apparatus of claim 3, wherein the first andsecond waveguides are operable to convey the virtual image to thecorresponding left and right eye of the viewer.
 9. The apparatus ofclaim 8, wherein the actuator is operable to adjust a relative angulardisposition of the first and second waveguide relative to the frame. 10.The apparatus of claim 2, further comprising at least one imagegenerator, wherein the adjustment mechanism is operable to relativelyshift left-eye image content and right-eye image content produced by theat least one image generator in response to the output signal of the atleast one sensor.
 11. An imaging apparatus for stereoscopic viewing,comprising: a flexible frame operable to be reshaped from a first shapeto a second shape; a left-eye imaging apparatus including a leftprojection system and a left waveguide; and a right-eye imagingapparatus including a right projection system and a right waveguide;wherein the left-eye imaging apparatus and the right-eye imagingapparatus have a relative alignment operable to convey stereoscopicvirtual images to the viewer when the frame is in the first shape; theleft-eye imaging apparatus and the right-eye imaging apparatus beingrigidly coupled to each other within the frame, wherein the frame isoperable to flex relative to the left-eye imaging apparatus and theright-eye imaging apparatus; and wherein the left-eye imaging apparatusand the right-eye imaging apparatus maintain the relative alignment whenthe frame is in the second shape.
 12. The apparatus of claim 11, whereinthe flexible frame includes a flexible nose bridge located between theleft-eye imaging apparatus and the right-eye imaging apparatus.
 13. Theapparatus of claim 12, wherein the left-eye imaging apparatus and theright-eye imaging apparatus are connected to the frame through a pin inthe flexible nose bridge.
 14. The apparatus of claim 11, wherein theflexible frame includes cavities within which the left-eye imagingapparatus and the right-eye imaging apparatus are relatively movablewith respect to the frame.
 15. A near-eye binocular imaging system,comprising: at least one image generator operable to generate angularlyencoded image-bearing beams; a frame configured to be worn by a viewer,wherein the frame is operable to be reshaped from a first shape to asecond shape; a left-eye imaging apparatus comprising a first waveguidesupported by the frame, wherein the left-eye imaging apparatus isoperable to convey at least a portion of the image-bearing beams to aleft eye of the viewer; a right-eye imaging apparatus comprising asecond waveguide supported by the frame, wherein the right-eye imagingapparatus is operable to convey at least a portion of the image-bearingbeams to a right eye of the viewer; wherein the left-eye imagingapparatus and the right-eye imaging apparatus have a first relativealignment operable to convey stereoscopic virtual images to the viewerwhen the frame is in the first shape; wherein the left-eye imagingapparatus and the right-eye imaging apparatus are arranged at a secondrelative alignment when the frame is in the second shape; a sensorsupported by the frame, wherein the sensor is operable to detect thechange in the relative orientation of the left-eye imaging apparatus andthe right-eye imaging apparatus; and a processor associated with the atleast one image generator, wherein the processor is operable to receivean output from the sensor and determine an amount of adjustment operableto compensate for the changes to the relative orientation of theleft-eye imaging apparatus and the right-eye imaging apparatus, andwherein the processor is operable to adjust the angular encoding of theimage-bearing beams to at least partially restore the relative alignmentof the stereoscopic virtual images viewable by the left and right eyesof the viewer while the frame is in the second shape.
 16. The near-eyebinocular imaging system of claim 15, wherein the at least one imagegenerator comprises a first projector supported by the frame, whereinthe first projector is operable to project the angularly encodedimage-bearing beams into the first waveguide, and wherein the firstwaveguide is operable to convey at least a portion of the angularlyencoded image-bearing beams to the viewer's left eye.
 17. The near-eyebinocular imaging system of claim 16, wherein the at least one imagegenerator comprises a second projector supported by the frame; andwherein the second projector is operable to project the angularlyencoded image-bearing beams into the second waveguide, and wherein thesecond waveguide is operable to convey at least a portion of theangularly encoded image-bearing beams to the viewer's right eye.
 18. Thenear-eye binocular imaging system of claim 17, wherein the processor isoperable to adjust the angular encoding of the image-bearing beams of atleast one of the first and second projectors to convey stereoscopicvirtual images to the viewer.
 19. The near-eye binocular imaging systemof claim 18, wherein the frame is subject to flexure to accommodatedifferent viewer head anatomies and the sensor is operable to measurethe flexure of the frame.
 20. The near-eye binocular imaging system ofclaim 19, wherein the sensor includes at least one of a camera and adistance sensor mounted on the frame operable to measure the flexure ofthe frame.
 21. The near-eye binocular imaging system of claim 19,wherein the frame includes a frame front supporting the first and secondwaveguides, and temples supporting the first and second projectors. 22.The near-eye binocular imaging system of claim 21, wherein the framefront includes a nose-piece section between the first and secondwaveguides, and the sensor is operable to detect flexure of thenose-piece section.
 23. The near-eye binocular imaging system of claim21, wherein the sensor is one of at least two sensors operable to detectchanges in the orientation of the temples with respect to the framefront.
 24. The near-eye binocular imaging system of claim 15, furthercomprising an adjustment mechanism operable to respond to the reshapingof the frame, wherein the adjustment mechanism is operable to change anangular alignment of the first waveguide and/or the second waveguiderelative to the at least one image generator and to the frame, whereinthe processor is operable to output a signal to the adjustment mechanismto change the angular alignment of the first waveguide and/or the secondwaveguide to at least partially restore relative alignment of theleft-eye imaging apparatus and the right-eye imaging apparatus while theframe is in the second shape.
 25. A method of accommodating flexure of aframe that supports a left-eye imaging apparatus and a right-eye imagingapparatus within which angularly encoded image-bearing beams generatedby at least one image generator are conveyed to the left and right eyesof a viewer, comprising: relatively orienting the left-eye imagingapparatus and the right-eye imaging apparatus for relatively aligningvirtual images viewable by the left and right eyes of the viewer toconvey stereoscopic virtual images to the viewer when the frame is in afirst shape; reshaping the frame whereby a relative orientation of theleft-eye imaging apparatus and the right-eye imaging apparatus isoperable to change to accommodate different viewer head anatomies whilecorrespondingly misaligning the virtual images viewable by the left andright eyes of the viewer, wherein the frame is in a second shape;sensing the reshaping of the frame as an indication of the change in therelative orientation of the left-eye imaging apparatus and the right-eyeimaging apparatus; determining from the sensed reshaping of the frame anamount of adjustment to compensate for the changes to the relativeorientation of the left-eye imaging apparatus and the right-eye imagingapparatus while the frame is in the second shape; and adjusting theangular encoding of the image-bearing beams that are generated by the atleast one image generator in accordance with the determined amount ofadjustment to at least partially restore the relative alignment of thestereoscopic virtual images while the frame is in the second shape. 26.The method of claim 25, wherein the step of reshaping includes bending anose-piece portion of the frame between the left-eye and right-eyeimaging apparatus and the step of sensing detects the bending of thenose-piece section.
 27. The method of claim 25, wherein the at least oneimage generator includes a first image generator operable to generateangularly encoded image-bearing beams directed to the left-eye imagingapparatus, and a second image generator operable to generate angularlyencoded image-bearing beams directed to the right-eye imaging apparatus,and the step of adjusting the angular encoding of the image-bearingbeams includes adjusting the angular encoding of the image-bearing beamsgenerated by the first and second image generators in oppositedirections.